In recent years, a portable phone is widespread with the advance of communications technology. It is expected that a moving image will be transferred and more amount of information will be transmitted in the days ahead. Meanwhile, a personal computer for mobile use is produced due to the weight reduction. An information terminal which is called a PDA originated in an electronic data book is produced a lot and being widespread. In those portable information devices, a lot of semiconductor devices such as a CPU (Central Processing Unit) are used.
There are various kinds of semiconductor devices. FIG. 10 shows a block diagram of a CPU as an example. A CPU 1001 shown here is formed of a timing control circuit 1002, an instruction analysis decoder 1003, a register array 1004, an address logic buffer circuit 1005, a data bus interface 1006, an ALU 1007, an instruction register 1008 and the like.
Now, each circuit is briefly described. The timing control circuit receives an instruction externally, converts it into data for internal use, and sends it to other blocks. Further, in accordance with an internal operation, the timing control circuit gives an external portion an instruction such as a read and write of memory data. The instruction analysis decoder 1003 plays a role to convert an external instruction into an instruction for internal use. The register array 1004 is a volatile memory which stores data temporarily. The address logic buffer 1005 is a circuit which specifies an address of an external memory. The data bus interface 1006 is a circuit which puts data into and out of a device such as an external memory or a printer. The ALU 1007 is a circuit which provides an arithmetic operation. The instruction register 1008 is a circuit which stores an instruction temporarily. A CPU is formed by a combination of such circuits.
A semiconductor device such as a CPU these days use an insulator for a substrate instead of a silicon substrate. Such a semiconductor device is called an SOI (Silicon On Insulator) and presently being developed. By using an insulator as a substrate, a parasitic capacitance between a transistor and the substrate is reduced, thus a high speed and a power reduction can be achieved. In particular, it is used for a portable electronic device by virtue of the power reduction. An electronic device using a semiconductor device which consumes much power has problems that a large battery and a cooling fan are required, leading to a problem that an electronic device itself becomes large.
In view of the aforementioned, a composite type semiconductor device is suggested which has a structure that a wiring substrate and a package are attached so as to satisfy a high thermal conductivity and low modulus.
[Patent Document 1]
Japanese Patent Laid-Open No. Hei 7-74282
Moreover, FIG. 11 shows an example of a circuit having two stages of inverters of a semiconductor device using a conventional silicon substrate. In this example, the inverter circuits are formed of P-ch transistors 1102 and 1104, and N-ch transistors 1101 and 1103.
FIG. 12 shows an example of a circuit having two stages of inverters of a semiconductor device using an SOI substrate. In this example, the inverter circuits are formed of P-ch transistors 1202 and 1204, and N-ch transistors 1201 and 1203.